1. Field of the Invention
The present invention relates in general to data communications peripherals and more particularly to a system and a method for wireless data transfer between a computer and a telephone line using a remote media interface.
2. Background Art
Data communications peripherals such as modems are important and ubiquitous devices that allow a computer to transmit and receive data over telephone lines. Data may include text, sounds, images and video. The word xe2x80x9cmodemxe2x80x9d is a concatenation of modulator and demodulator. In general, a modem operates by taking a digital data stream and converting the digital data into a modulated analog signal for transmission over the telephone line. Because most telephone lines are designed to transmit only analog information the modulator in the modem ensures that the modulated analog signal conforms to the voice-like signal requirements of the telephone line. The demodulator is a complementary device that converts the modulated analog signal into a digital data stream.
A typical modem is made up of a several components that are used for both transmission and reception. For example, the transmission of data over a telephone line begins in data terminal equipment (DTE). The DTE, which is an interface between the computer and the modem, converts user input into digital data streams for transmission and vice versa. The DTE includes control logic, buffer and one or more input and output devices to the computer and essentially controls the flow of data in or out of the computer.
The digital data stream from the DTE then flows into the digital signal processor (DSP). The DSP, also known as a data pump, contains signal processing algorithms that manipulate and convert the digital data from a digital data stream into a modulated analog signal and vice versa. A controller, which is generally a microprocessor having storage media, is used for control, buffering and processing by the DTE and DSP.
After processing by the DSP the modulated analog signal is received by a data access arrangement (DAA). The DAA is data communications equipment that is furnished or approved by a common carrier (for example, a telephone company) that permits the attachment of privately owned data terminal and communications equipment to the common carrier""s network. Typically the DAA is an impedance matching device that acts as an electrical interface converter to convert the modulated analog signal into a signal compatible with local telephone lines. In addition, the DAA contains protection circuitry to safeguard the modem components from damage by the telephone line and vice versa. Because the DAA is the interface between the user""s computer and the common carrier""s network the DAA is usually the only part of the modem subject to government regulation. The DAA must meet the local requirements and regulations before it can be certified for use in the modem.
Electrical power required to operate the modem components generally comes from the computer""s power supply, battery or AC outlet. Each modem component requires some electrical power and any reduction in the number of modem components helps to decrease the power drain on the computer""s electrical power source.
The data transmission is completed by sending the modulated analog signal from the DAA to the telephone line using, for example, a registered jack-11 (RJ-11) connector. When data is received from the telephone line the flow through these modem components is reversed and the modem demodulates the incoming modulated analog signal into digital data.
Traditionally these modem components have been hardware. But the steadily increasing microprocessing power of computers has made possible the use of software to perform the functions of most modem components. These soft modems, as they are known, provide numerous advantages over the conventional hardware modems. One advantage of a soft modem is that the majority of hardware associated with a modem are eliminated making the soft modem less complicated, more economical and more reliable. Another advantage of a soft modem is that feature updates and bug fixes can be provided by simply downloading patches from a bulletin board service (BBS) or the worldwide web (WWW), thus eliminating the inconvenience of having to update the flash memory on the printed circuit board of the modem. Soft modems also decrease the drain on the computer""s electrical power source because some hardware components are eliminated. In a true soft modem the DSP components of the modem are all software and the controller functions are performed by the computer""s central processing unit (CPU). Because the DAA is an impedance matching device and contains protection circuitry, however, the DAA must be hardware.
This requirement that the DAA must be hardware also simplifies the regulatory and certification process of the modem. With a soft modem, the manufacturer can concentrate on configuring the DAA to meet the local regulations without involving other modem components. Moreover, the regulatory and certification process is simplified because the DAA by itself has a ringer equivalent number (REN) equal to one. The REN is a measure of how much power a device draws from the telephone line, and the DAA has a REN equal to other devices such as telephones, fax machines and answering machines.
One disadvantage of existing conventional and soft modems is that, as mentioned above, the DAA must be hardware and thus still requires electrical power to operate. When the modem is located on a portable computer such as, for example, a notebook computer or a personal digital assistant (PDA), this power consumption by the DAA can severely drain and shorten battery life. In a personal computer (PC) or any host computer (HC) this power consumption by the DAA can lead to higher operating temperatures and can impose additional cooling requirements that increase the cost, the complexity and the size of the computer.
Another disadvantage of existing modems is that they must be xe2x80x9ctetheredxe2x80x9d to telephone line by a telephone cable. This tethering severely restricts the portability of all types of computers, especially the conventional PC and the portable computers. For example, is it quite difficult to relocate the computer any more than a short distance from the telephone jack because of this tethering requirement. For these reasons there exists a need for a modem that retains all the advantages of a soft modem while reducing the power burden and eliminating the tethering restrictions on the computer.
To overcome the limitations in the prior art as described above and other limitations that will become apparent upon reading and understanding the present specification, the present invention includes a system and method for wireless data transfer between a computer and a telephone line using a remote media interface (RMI). The system and method of the present invention require less power from the computer and are not connected by cables to the computer. As a result battery life of a portable computer is greatly increased (because less power is drawn from the computer) and the portability of a desktop computer is enhanced (because there is no cabling between the computer and the telephone line). Current modems draw a great deal of power from the computer which significantly shortens a portable computer""s battery life. In addition, current modems require cabling between the computer and the telephone line which severely restricts the computer""s portability.
The system of the present invention includes a remote media interface (RMI) for transferring data between a computer and a telephone line. The RMI and the computer are physically separate and in bi-directional wireless communication using infrared (IR) transceivers. In a preferred embodiment, the majority of modem components are located in the computer (either as hardware or software) and the only modem component included in the RMI is a data access arrangement (DAA) and possibly a codec. The DAA converts data from the computer (such data in digital form) into a signal that can be transmitted over the telephone lines. The DAA requires electrical power to operate and locating the DAA off the computer eliminates this power burden from the computer. The RMI can be located near an electrical outlet and a telephone jack while the computer can be located virtually anywhere within the range of the IR transceiver. The telephone cable between the computer and the telephone jack is completely eliminated and vastly enhances the portability of the computer.
The present invention also includes a method of wireless transfer of data between a computer and a telephone line using the RMI and the wireless data transfer system. Other aspects and advantages of the present invention as well as a more complete understanding thereof will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Moreover, it is intended that the scope of the invention be limited by the claims and not the preceding summary or the following detailed description.